HTML代码区域
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
table{
border-right: 1px solid black;
border-bottom: 1px solid black;
width: 500px;
height: 500px;
}
td{
border-top: 1px solid black;
border-left: 1px solid black;
}
</style>
</head>
<body>
<table>
<tr>
<td>1</td>
<td>2</td>
<td>3</td>
</tr>
<tr>
<td>4</td>
<td>5</td>
<td>6</td>
</tr>
<tr>
<td>7</td>
<td>8</td>
<td>9</td>
</tr>
</table>
</body>
JavaScript代码区
<script>
//通过标签名找到td 返回一个数组
var td = document.getElementsByTagName("td");
//定义循环取到每一个td元素
for(let i =0; i<9; i++){
//鼠标移到上面背景变成红色
td[i].onmouseover = function(){
td[i].style.backgroundColor = "red";
}
//鼠标移出变成白色
td[i].onmouseout = function(){
td[i].style.backgroundColor = "white";
}
}
</script>
想问的问题是 当我把for循环里面的let换成var时会报错(如下图)
1.请问这是为什么?
2.请问let和var的区别?